<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>

    <script>
        // 1.定义变量
        var num = 1;
        var name = "zhourui";
        // 2.条件控制
        var score = 87;
        if(score > 60 && score <= 70){
            alert("60 ~ 70");
        }else if(score > 70 && score <= 80){
            alert("70 ~ 80");
        }else{
            alert("优秀。")
        }
    </script>

</head>
<body>

</body>
</html>